ARC Perm-Squeeze RDF - A Permeable Plug Forming Rapidly Dehydrating Fluid

ABSTRACT

A rapidly dehydrating lost circulation material (LCM) composition that forms a permeable plug is provided. The LCM composition may include a carrier fluid, a clay particulate material, a viscosifier, and date tree waste fibers. The carrier fluid may be water and the viscosifier may be a cellulosic microfiber. The LCM composition may mitigate or prevent lost circulation by forming a plug in a fracture of the lost circulation zone and may also enable the production of hydrocarbons from the zone without removal of the plug via an acid treatment. Methods of lost circulation control and manufacture of the rapidly dehydrating LCM are also provided

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority from U.S.Non-provisional application Ser. No. 15/815,159 filed Nov. 16, 2017, andtitled “ARC PERM-SQUEEZE RDF—A PERMEABLE PLUG FORMING RAPIDLYDEHYDRATING FLUID,” a copy of which is incorporated by reference in itsentirety for purposes of United States patent practice.

BACKGROUND Field of the Disclosure

The present disclosure generally relates to controlling lost circulationin a wellbore during drilling with a drilling fluid. More specifically,embodiments of the disclosure relate to a lost circulation material(LCM).

Description of the Related Art

Lost circulation is one of the frequent challenges encountered duringdrilling operations. Lost circulation can be encountered during anystage of operations and occurs when some or all of the drilling fluid(which may include drilling mud) pumped into a well does not return tothe surface. While a de minimis amount of fluid loss is expected,excessive fluid loss is not desirable from a safety, economical, orenvironmental point of view. Lost circulation is associated withproblems with well control, borehole instability, pipe sticking,unsuccessful production tests, poor hydrocarbon production after wellcompletion, and formation damage due to plugging of pores and porethroats by mud particles. In extreme cases, lost circulation problemsmay force abandonment of a well.

SUMMARY

Different types of traditional and specially designed loss controlmaterials, slurries, and pills are used to control lost circulation.Loss control materials may generally be classified into severalcategories, such as surface plastering and shallow plugging materials,fracture sealing and deeper plugging materials (also referred to as“loss control slurries”), and interstitial bridging and pore pluggingmaterials. Such lost circulation materials (LCMs) are used to mitigatethe lost circulation by blocking the path of the drilling mud into theformation. The type of LCM used in a lost circulation situation dependson the extent of lost circulation and the type of formation.

Lost circulation may occur in the non-reservoir and reservoir sectionsof a wellbore. Controlling loss of circulation in reservoir sectionsusing conventional LCMs may cause permanent sealing and plugging of thepermeable channels and fractures, thus preventing production of oil andgas resources through these permeable channels and fractures andimpacting the ultimate productivity of the well and the field.Consequently, certain LCMs may be more suitable for use in reservoirsections. For example, LCMs that are acid soluble are typically used inreservoir sections. However, the acid solubility of LCMs may onlyprovide partial, or some instances, no restoration of the flowcharacteristics of original fractures and channels. First, the acidsused to dissolve such LCMs may only react with the face of a plug, oronly up to certain depth, and may not have any effect beyond about 25millimeters (mm) to about 50 mm of the plug due to the escape of theacid to the wellbore zones with the lowest flow resistance. As a result,the barrier causing the flow restriction may remain in the permeablechannels and fractures even after an acid treatment. Second, the acidtreatment may produce a reaction byproduct that may precipitate andsettle in the pores, pore throats, permeable channels and fractures withcomplete or partial blockage of these flow conduits. In some instances,the acid treatment may cause more damage than the LCM treatment itself.

In one embodiment, a lost circulation material (LCM) composition isprovided. The LCM composition includes a carrier fluid, a particulatematerial includes a clay, a viscosifier, and, a fibrous material thatincludes date tree waste fibers. In some embodiments, the carrier fluid,the particulate material, the viscosifier, and the fibrous material forma homogenous mixture. In some embodiments, the carrier fluid includeswater. In some embodiments, the viscosifier includes a cellulosicmicrofiber. In some embodiments, the date tree waste fibers include datetree rachis fibers, date tree leaf fibers, or a combination thereof. Insome embodiments, the clay includes calcium montmorillonite clay. Insome embodiments, the calcium montmorillonite clay is an amount in therange of 3 weight % of the total weight (w/w %) to 6 w/w % of the LCMcomposition. In some embodiments, the date tree waste fibers is anamount in the range of 6 weight % of the total weight (w/w %) to 9 w/w %of the LCM composition. In some embodiments, the LCM composition has adehydration time of less than 12 minutes at 100 pounds-per-square inchdifferential (psid) pressure. In some embodiments, the LCM compositionhas a dehydration time of less than 1 minutes at 500 pounds-per-squareinch differential (psid) pressure.

In another embodiment, a method to control lost circulation in a lostcirculation zone in a wellbore is provided. The method includesintroducing an altered drilling fluid into the wellbore such that thealtered drilling fluid contacts the lost circulation zone and reduces arate of lost circulation into the lost circulation zone, wherein thealtered drilling fluid comprises a drilling fluid and a lost circulationmaterial (LCM) composition. The LCM composition includes a carrierfluid, a particulate material includes a clay, a viscosifier, and, afibrous material that includes date tree waste fibers. In someembodiments, the method includes adding the LCM composition to thedrilling fluid to create the altered drilling fluid. In someembodiments, the carrier fluid, the particulate material, theviscosifier, and the fibrous material form a homogenous mixture. In someembodiments, the carrier fluid includes water. In some embodiments, theviscosifier includes a cellulosic microfiber. In some embodiments, thedate tree waste fibers include date tree rachis fibers, date tree leaffibers, or a combination thereof. In some embodiments, the clay includescalcium montmorillonite clay. In some embodiments, the calciummontmorillonite clay is an amount in the range of 3 weight % of thetotal weight (w/w %) to 6 w/w % of the LCM composition. In someembodiments, the date tree waste fibers is an amount in the range of 6weight % of the total weight (w/w %) to 9 w/w % of the LCM composition.

In some embodiments, an altered drilling fluid is provided. The altereddrilling fluid includes a drilling fluid and a lost circulation material(LCM) composition. The LCM composition includes a carrier fluid, aparticulate material includes a clay, a viscosifier, and, a fibrousmaterial that includes date tree waste fibers. In some embodiments, thecarrier fluid includes water. In some embodiments, the viscosifierincludes a cellulosic microfiber. In some embodiments, the date treewaste fibers include date tree rachis fibers, date tree leaf fibers, ora combination thereof. In some embodiments, the clay includes calciummontmorillonite clay. In some embodiments, the calcium montmorilloniteclay is an amount in the range of 3 weight % of the total weight (w/w %)to 6 w/w % of the LCM composition. In some embodiments, the date treewaste fibers is an amount in the range of 6 weight % of the total weight(w/w %) to 9 w/w % of the LCM composition.

In some embodiments, a method of forming a lost circulation material(LCM) composition is provided. The method includes adding a carrierfluid to form a mixture, adding a particulate material to the mixture,the particulate material comprising a clay, adding viscosifier to themixture, and adding a fibrous material to the mixture, the fibrousmaterial comprising date tree waste fibers. In some embodiments, the LCMcompositions forms a homogenous mixture. In some embodiments, thecarrier fluid includes water. In some embodiments, the viscosifierincludes a cellulosic microfiber. In some embodiments, the date treewaste fibers include date tree rachis fibers, date tree leaf fibers, ora combination thereof. In some embodiments, the clay includes calciummontmorillonite clay

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph of fibers produced from the date tree waste inaccordance with an embodiment of the disclosure;

FIG. 2 is a block diagram of a process for preparing and using a rapidlydehydrating LCM composition in accordance with an embodiment of thedisclosure;

FIG. 3 is a photograph of a plug formed in a test cell after adehydration test of an example rapidly dehydrating LCM composition inaccordance with an embodiment of the disclosure;

FIG. 4 is a photograph of a plug formed in a test cell after adehydration test of an example rapidly dehydrating LCM compositionsimulating relatively large fractures bounded by a formation having arelatively high permeability; and

FIG. 5 is a photograph of a plug formed in a Permeability PluggingTester (“PPT”) cell after a dehydration test of an example rapidlydehydrating LCM composition in accordance with an embodiment of thedisclosure.

DETAILED DESCRIPTION

The present disclosure will be described more fully with reference tothe accompanying drawings, which illustrate embodiments of thedisclosure. This disclosure may, however, be embodied in many differentforms and should not be construed as limited to the illustratedembodiments. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art.

As a wellbore is drilled, a drilling fluid is continuously pumped intothe wellbore to clear and clean the wellbore and the filings. Thedrilling fluid is pumped from a mud pit into the wellbore and returnsagain to the surface. A lost circulation zone is encountered when theflow rate of the drilling fluid that returns to the surface is less thanthe flow rate of the drilling fluid pumped into the wellbore, and it isthis reduction or absence of returning drilling fluid that is referredto as lost circulation.

The present disclosure includes compositions for use as a lostcirculation material (LCM) to mitigate or prevent such lost circulationin a well and prevent or reduce the loss of drilling mud while drilling.The compositions described in this disclosure may create a plug in afracture of a formation to reduce or prevent the loss of drilling mudinto the surrounding formation and enable production of hydrocarbonswithout removal of the plug (for example, via an acid treatment). Theplug formed by the LCM compositions described in the disclosure may haveporosity-permeability (“poro-perm”) characteristics similar to formationrock to provide for the infiltration of hydrocarbons through the plugmatrix and enable production of hydrocarbons from the formation withoutremoving the plug. Further, the compositions described in thisdisclosure are eco-friendly, non-toxic, and environmentally safe suchthat the use of such compositions for lost circulation control will havelittle to no detrimental effects on the subsurface environment andsurrounding aquifers.

Additionally, the compositions described in this disclosure use rawmaterials that may be available locally and may encourage economic andjob growth of local industries, such as the date farming industry. Thecompositions described in the disclosure also provide a viable recyclingpath for date tree waste (that is, portions of the date tree discardedafter production of dates). Further, the production of compositions fromlocally available raw materials may reduce or eliminate the importationof conventional LCMs.

The present disclosure includes rapidly dehydrating LCM compositions tocontrol lost circulation in a lost circulation zone in a wellbore. Insome embodiments, a rapidly dehydrating LCM composition includes acarrier fluid, a clay particulate material, a viscous material (alsoreferred to as a “viscosifier”), and date tree waste fibers as a fibrousmaterial. In some embodiments, the rapidly dehydrating LCM compositionincludes water as the carrier fluid, a calcium montmorillonite clay asthe particulate material, a cellulosic microfiber viscosifier, and datetree rachis and leaf fibers produced from date trees (also referred toas “date palms”) as the fibrous material. FIG. 1 is a photograph 100 offibers produced from the date tree waste in accordance with anembodiment of the disclosure. As used in the disclosure, the term datetree waste refers to the waste produced from processing date trees (alsoreferred to as “date palms”) in the production of date fruits (alsoreferred to as “dates”). The fibers may include, by way of example,fibers produced from date tree rachis (also referred to as “date treerachis fibers”) and fibers produced from date tree leaves (also referredto as “date tree leaf fibers”). In some embodiments, the LCM compositionmay form or be referred to as a rapidly dehydrating fluid (RDF). As willbe appreciate, the plug may be used in reservoir zones and non-reservoirzones.

Rapidly Dehydrating LCM Compositions and Processes

In some embodiments, a rapidly dehydrating LCM (also referred to as aloss control slurry) may include a carrier fluid, a fibrous material, aclay particulate material, and a viscosifier. The carrier fluid mayinclude freshwater, seawater, brines, brackish water, or formationfluid. The fibrous material may include a fibrous material derived fromdate tree waste, such as date tree rachis fibers and date tree leaffibers. In some embodiments, the clay particulate material may includecalcium montmorillonite clay. The viscosifier may include a suitablecommercial viscosifier that can provide for rapid dehydration of theslurry at about 100 pounds-per-square inch differential (psid) to about500 psid overbalance pressure. In some embodiments, the fibrous materialmay include date tree rachis fibers and date tree leaf fibers.

In some embodiments, a rapidly dehydrating LCM composition may include acarrier fluid, a clay particulate material, a viscosifier, and date treerachis fibers. In some embodiments, a rapidly dehydrating LCMcomposition may include a carrier fluid, a clay particulate material, aviscosifier, and date tree leaf fibers. In some embodiments, a rapidlydehydrating LCM composition may include a carrier fluid, a clayparticulate material, a viscosifier, date tree leaf fibers, and datetree leaf fibers.

In some embodiments the carrier fluid may include water. For example,the carrier fluid may include freshwater (water having relatively low(that is, less than 5000 parts-per-million by mass (ppm)) concentrationsof total dissolved solids (TDS)), seawater (for example, water having asalinity in the range of about 30,000 to about 40,000 ppm TDS),artificial brines, natural brines, brackish water, or formation water.

In some embodiments, the particulate material of the LCM composition mayinclude a clay. In some embodiments, the clay may be calciummontmorillonite clay. In some embodiments, the particulate material ofthe LCM composition may include calcium montmorillonite clay particleshaving a particle size of greater than about 25 microns. In someembodiments, the clay-based particulate material of the LCM compositionmay be Rev Dust® manufactured by Milwhite Inc., of Brownsville, Tex.,USA. In some embodiments, the clay particulate material may includedrill solids (that is, solid particles from a formation generated whiledrilling).

In some embodiments, the viscosifier may include a cellulosic microfiberderived from raw vegetable materials. In some embodiments, theviscosifier may be a non-toxic viscosifier having cellulose in the rangeof about 5 weight % of the total weight (w/w %) to about 25 w/w % andwater, and a pH in the range of about 6 to about 7. In some embodiments,the viscosifier may include Betafib® manufactured by Cosun BiobasedProducts of Roosendaal, Netherlands.

In some embodiments, a rapidly dehydrating LCM composition may includewater as a carrier fluid, calcium montmorillonite clay as a particulatematerial, a cellulosic microfiber as a viscosifier, and date tree rachisand leaf fibers as a fibrous material. In some embodiments, the calciummontmorillonite clay may be in the range of about 3 w/w % to about 6 w/w%. In some embodiments, the date tree rachis and leaf fibers may in therange of about 6 w/w % to about 9 w/w %. In some embodiments, theviscosifier may be in the range of about 2 w/w % to about 5 w/w %. Insome embodiments, when subjected to a squeezing or overbalance pressure,the rapidly dehydrating LCM composition may eliminate all of a fluidphase in 12 minutes or less at about 100 psid overbalance pressure orless than about 1 minute at 500 psid overbalance pressure.

In some embodiments, when subjected to a squeezing or overbalancepressure, the rapidly dehydrating LCM composition can form a permeableplug in a fracture to prevent or reduce the loss of drilling mud intothe surrounding formation and enable the production of hydrocarbonsthrough the fracture during production. In some embodiments, a rapidlydehydrating LCM composition may have a greater concentration of fibrousmaterial (for example, date tree rachis fibers) to form a plug having arelatively greater thickness, as compared to rapidly dehydrating LCMcomposition having lesser concentrations of the fibrous material.Advantageously, the plug formed by the rapidly dehydrating LCMcomposition does not need to be removed via an acid treatment (that is,by introducing acid into the wellbore) to move to the production phaseof a well. That is, a plug formed by the rapidly dehydrating LCMcomposition may have poro-perm characteristics similar to that offormation rock in the reservoir, thus enabling the production ofhydrocarbons through the plug matrix.

In some embodiments the fibrous material of the LCM composition mayinclude date tree rachis fibers (that is, a material composed of suchfibers) and date tree leaf fibers (that is, a material composed of suchfibers). The date tree rachis and leaves may be obtained from date treewaste, such as produced as a waste by-product from date processing, datetree pruning, or both. In some embodiments, the date tree waste may beobtained from date processing plants to provide sustainable source ofparticulate material. Moreover, local sources of date tree waste mayreduce the cost of imported LCM products, components, or both. In someembodiments, the date tree waste may be obtained from the speciesphoenix dactylifera. It should be appreciated that, in some embodiments,the date tree waste may be obtained from genetically modified date trees(that is, genetically modified organisms (GMOs)). In some embodiments,the date tree rachis and leaves may be prepared by cleaning the rachisand leaves, such as by blowing air over the rachis and leaves to removedust, rubbish, and other material, and then chopping, crushing, andgrinding the rachis and leaves using an industrial grinder to producedate tree rachis fibers and date tree leaf fibers. In some embodiments,the processed fibers may be sifted via a sieve to obtain a desired sizeof the fibrous material for use in the LCM composition described in thedisclosure.

In some embodiments, the date tree rachis and leaf fibers may includeuntreated date tree rachis and leaf fibers, thus preserving theenvironmentally-friendly and biodegradable properties of themanufacturing process, the fibers, and the resulting LCM composition. Asused in the disclosure, the term “untreated” or “without treating”refers to not treated with alkali or acid, not bleached, not chemicallyaltered, not oxidized, and without any extraction or reaction processother than possibly drying of water. The term “untreated” or “withouttreatments” does not encompass grinding or heating to remove moisturebut does encompass chemical or other processes that may change thecharacteristics or properties of the fibers. In such embodiments, thedate tree fibers may be manufactured without treating before, during, orafter crushing, grinding, drying, or any other processing.

In some embodiments, a rapidly dehydrating LCM composition may be formedby adding a carrier fluid to a mixture, adding the clay-basedparticulate material (for example, calcium montmorillonite clay) to themixture, adding a viscosifier to the mixture, and adding a fibrousmaterial (for example, date tree rachis fibers, date tree leaf fibers,or both) to the mixture. In some embodiments, the rapidly dehydratingLCM composition may be formed by first adding the carrier fluid,followed by adding the clay-based particulate material (for example,calcium montmorillonite clay), followed by adding the viscosifier, andfollowed by adding a fibrous material (for example, date tree rachisfibers, date tree leaf fibers, or both). The LCM composition may beformed by mixing the carrier fluid, particulate material, viscosifier,and fibrous material in a high-speed mixer (for example, a commercialdrilling fluid mixer) and forming a homogenous mixture, such as ahomogenous fluid pill. In some embodiments, the LCM composition may bemixed for a time period (for example, in a range of about 1 minutes toabout 5 minutes) after the addition of each component. In someembodiments the rapidly dehydrating LCM composition may be producedwithout any additives or treatments, thus preserving theenvironmentally-friendly and biodegradable properties of both themanufacturing process and the rapidly dehydrating LCM composition. Inother embodiments, the rapidly dehydrating LCM composition may be mixedor otherwise combined with additives or otherwise treated. In someembodiments, additives may be mixed or otherwise combined with the LCMto change the rheology or pH of the LCM. In some embodiments, suchadditives may include softening agents, surface active agents(surfactants), viscosity agents, thinning agents, dispersants, coatings(for example, pellet coatings), pH modifiers, insecticides, biocides, orany suitable combination thereof.

FIG. 2 depicts a process 200 for preparing and using a rapidlydehydrating LCM composition in accordance with an embodiment of thedisclosure. Initially, the rapidly dehydrating LCM composition may beformed from a carrier fluid, a clay particulate material, a viscosifier,and date tree waste fibers (for example, date tree rachis fibers, datetree leaf fibers, or both) (block 202). For example, in someembodiments, the rapidly dehydrating LCM composition may be formed byfirst adding the carrier fluid, followed by adding the clay particulatematerial (for example, calcium montmorillonite clay)), followed byadding the viscosifier, and followed by adding a fibrous material (forexample, date tree rachis fibers, date tree leaf fibers, or both), andmixing in a high-speed mixer (for example, a commercial drilling fluidmixture) and forming a homogenous mixture. In some embodiments, the LCMcomposition may be mixed for a time period (for example, in a range ofabout 1 minutes to about 5 minutes) after the addition of each componentand mixed for another time period after all components have been addedto form an LCM pill (that is, a fluid pill formed of the LCMcomposition).

The LCM pill may be added to a drilling fluid, such as a drilling mud(block 204). For example, in some embodiments, the LCM pill may be addedto (for example, blended with) an oil-based drilling mud or awater-based drilling mud. In some embodiments, an altered drilling fluidmay be formed having the LCM pill. In some embodiments, the LCM pill maybe added at the mud pit of a mud system. After addition of the LCM pill,the drilling fluid having the LCM pill (that is, an altered drillingfluid) may be circulated at a pump rate effective to position the LCMpill into contact with a lost circulation zone in a wellbore (block206). Next, a pressure may be applied to form one or more plugs from theLCM pill, such that the rapidly dehydrating LCM composition of the pillalters the lost circulation zone by forming one or more plugs in thepaths, cracks, and fractures in a formation in the lost circulationzone. For example, in some embodiments the plugs may form in less thanabout 12 minutes at a pressure of about 100 psid. In some embodiments,the plugs may form in less than about 1 minute at a pressure of about500 psid. It should be appreciated that the time period for formation ofthe plugs may be also be based on the type of formation (for example,the size of the paths, cracks, and fractures in the formation).

The plugs formed by the LCM composition may be retained during theproduction phase of the well (block 208). Advantageously, the retentionof the plugs avoids the use and introduction of acid (for example,hydrochloric acid) in the wellbore (referred to as “an acid treatmentjob”). Hydrocarbons may be produced from the lost circulation zonehaving the permeable plugs such that the plugs prevent the loss of wholemud during the drilling phase do not need to be removed during theproduction phase. As noted in the disclosure, the eco-friendly,non-toxic, and environmentally friendly properties of the rapidlydehydrating LCM composition may minimize or prevent any environmentalimpact, any effect on ecosystems, habitats, population, crops, andplants surrounding the drilling site where the rapidly dehydrating LCMcomposition is used. Moreover, the elimination of the use of acid toremove the plugs and being production from the well further minimizes orprevents further environment impact on ecosystems, habitats, population,crops, and plants surrounding the drilling site

EXAMPLES

The following examples are included to demonstrate embodiments of thedisclosure. It should be appreciated by those of skill in the art thatthe techniques and compositions disclosed in the example which followsrepresents techniques and compositions discovered to function well inthe practice of the disclosure, and thus can be considered to constitutemodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or a similar result without departing from the spirit and scope ofthe disclosure.

The following non-limiting examples of LCM compositions were preparedand evaluated to determine the rapidity of dehydration, the plug formingcapabilities, and the permeability of the formed plug. Table 1 shows theformulations of the example LCM compositions used in the tests, withcompositions of the components provided in milliliters (ml) or grams(g), and also expressed as weight of the total weight (w/w %) of the LCMcomposition:

TABLE 1 Example LCM formulation for testing Component Description AmountWater (ml) Carrier Fluid 350 Particulate Rev Dust ® 20 (4.8 w/w %)Material (g) Viscosifier (g) Betafib ® 15 (3.6 w/w %) Fibrous MaterialDate Tree Rachis 30 (7.2 w/w %) (g) and Leaf Fibers

As shown in Table 1, the example LCM formulation included a calciummontmorillonite clay, Rev Dust® manufactured by Milwhite Inc., ofBrownsville, Tex., USA. Rev Dust® is a non-reactive clay particulatematerial having a particle size greater than about 25 microns. Theexample formulation also includes a cellulosic microfiber viscosifier,Betafib®, manufactured by Cosun Biobased Products of Roosendaal,Netherlands. Each formulation also included a fibrous material of rachisfibers and leaf fibers obtained from the date tree phoenix dactylifera.

A fluid pill of the example LCM formulation was prepared by mixing eachcomponent into a mixture using a high speed mixer, in the order shown inTable 1: Rev Dust® was added to the carrier fluid in the mixture,followed by addition of the Betafib®, followed by addition of the datetree rachis and leaf fibers. The rapidity of dehydration of a fluid pillof the example LCM formulation was evaluated according to the testsdescribed infra.

The formulation was tested using an American Petroleum Society (API)filter press to simulate relatively large fractures bounded by aformation having a relatively low permeability. The API filter pressincludes a filtration cell to contain the LCM composition undergoingtesting. The formulation was testing using the following dehydrationtest procedure:

1. Install an API filter paper having a pore size of less than about 5microns into the API filter press;

2. Prepare formulation by mixing each component in a commercial drillingfluid mixer to form a homogenous mixture;

3. Fill filtration cell of API filter press with a 350 cubic centimeter(cc) pill of the formulation;

4. Mount filtration cell to API filter press, affix the top lid, andconnect an air pressure line of nitrogen gas at about 100 psid pressure;and

5. Measure the dehydration time of the pill (that is, the time for thefluid (about 350 cc) to be removed) at room temperature and 100 psidpressure and collect discarded fluid (that is, expelled carrier fluid)in a fluid collection pot at the bottom outlet of the API test cell.

The results of the dehydration tests are shown in Table 2, with thedehydration time measured in minutes (min) and the thickness of the plugformed by the dehydrated pill measured in mm:

TABLE 2 Results of Dehydration Test Simulating Relatively LargeFractures Bounded by a Formation Having a Relatively Low PermeabilityDehydration Test (100 psi Pressure, Room Temperature)-API Test ApparatusParameters Test-1 Test-2 Test-3 Dehydration Time 9.5 11 10 (min)Deposited Plug 40 38 39 Thickness (mm)

It was observed that immediately after application of the 100 psidpressure, 2-3 cc of spurt loss expelled from the API test cell. However,solids-free colored water exited the test cell after the initial spurtloss. The colored water was due to the de-coloration of the datetree-based fibers used in the example LCM formulation.

FIG. 3 is a photograph 300 of the plug formed in the test cell after thedehydration test according to the procedure described supra. As shown inTable 2, for a 350 cc pill in the API filtration cell under 100 psidifferential (psid) pressure, each formulation exhibited dehydrationtime of less than 3 minutes (that is, a solid plug was formed in 3minutes or less dehydration time under 100 psid pressure). As shown inFIG. 3, the shape of the plug deformed during the removal from the testcell. The prevention of the loss of whole mud after the initial spurtloss indicated that the plug formed by the example LCM formulation hasthe ability to prevent the loss of whole mud while drilling. Further,the infiltration of the fluid phase through the plug matrix indicatedthat the plug may enable the production of hydrocarbons via conductivefractures and permeable channels after completion of a well. Thus, theexample LCM formulation has the ability to create a plug havingporo-perm characteristics similar to rock to stop whole mud loss whiledrilling but enabling hydrocarbon production from conductive fracturesand super-K zones after completion of a well.

A diesel flow test was also conducted at 100 psid to predict thehydrocarbon production capability of the plug. After the dehydrationtest procedure described supra, a diesel flow test was performedaccording to the following procedure:

1. Release the pressure and remove the top lid of the API test cell.

2. Pour about 150 cc of diesel on top of the plug, affix the top lid,and connect the air pressure line of nitrogen gas at about 100 psidpressure; and

3. Collect the diesel pushed through the plug matrix in a fluidcollection pot at the bottom outlet of the API test cell.

The results of the diesel flow test are shown in Table 2, with thedehydration time measured in minutes (min) and the thickness of the plugformed by the dehydrated pill measured in mm:

TABLE 3 Results of Diesel Flow Time Test Diesel Flow Test (150 ccdiesel, 100 psi Pressure, Room Temperature)- API Test ApparatusParameters Test-1 Test-2 Test-3 Effluent Time (min) 8.3 8.5 9.3Deposited Plug 40 38 39 Thickness (mm)

As shown in Table 3, in each test the diesel exited the plug matrix inless than 10 minutes (other than the minimal amounts of diesel absorbedby the plug). The behavior of the diesel and plug matrix is similar tothe residual hydrocarbon in place of a reservoir. Thus, the example LCMformulation has the ability to form dual functional permeable plugshaving a first function of preventing the loss of whole mud whiledrilling and a second function of enabling hydrocarbon production fromconductive fractures and permeable channels having the formed plugs.

The formulation was also tested using the API filter press to simulaterelatively large fractures bounded by a formation having a relativelyhigh permeability. The formulation was testing using the followingdehydration test procedure to simulate relatively large fracturesbounded by a formation having a relatively high permeability:

1. Install a metal screen having a mesh size of 20 into the API filterpress to simulate a 250 micron pore size;

2. Prepare formulation by mixing each component in a commercial drillingfluid mixer to form a homogenous mixture;

3. Fill filtration cell of API filter press with a 350 cubic centimeter(cc) pill of the formulation;

4. Mount filtration cell to API filter press, affix the top lid, andconnect an air pressure line of nitrogen gas at about 100 psid pressure;and

5. Measure the dehydration time of the pill (that is, the time for thefluid (about 350 cc) to be removed) at room temperature and 100 psidpressure and collect discarded in a fluid collection pot at the bottomoutlet of the API test cell.

The results of the dehydration tests are shown in Table 4, with thedehydration time measured in minutes and the thickness of the plugformed by the dehydrated pill measured in mm:

TABLE 4 Results of Dehydration Test Simulating Relatively LargeFractures Bounded by a Formation Having a Relatively High PermeabilityDehydration Test (100 psi Pressure, Room Temperature)-API Test ApparatusParameters Test-1 Test-2 Test-3 Dehydration Time <1 <1 <1 (min)Deposited Plug 37 38 37 Thickness (mm)

It was observed that immediately after application of the 100 psidpressure, all of the carrier fluid expelled from the test cell as acloudy fluid, similar to a mud spurt. The cloudiness of the fluid slowlyreduced with the growth of the plug in the test cell. Due to the poorconsolidation of the plug at the test pressure and the 60 mesh sizescreen, the whole mud loss continued with a reduced rate of loss duringthe test. The reduced rate of whole mud loss indicates the whole mudloss mitigation ability of the example LCM formulation.

FIG. 4 is a photograph 400 of the plug formed in the test cell after thedehydration test simulating relatively large fractures bounded by aformation having a relatively high permeability described supra. Theinfiltration of the mud through the plug matrix indicates thepermeability of the plug. This permeability further indicates theability to create a plug having poro-perm characteristics similar torock to enable hydrocarbon production from conductive fractures andsuper-K zones after completion of a well.

A diesel flow test was also conducted at 100 psid to predict thehydrocarbon production capability of the plug, according to theprocedure described supra in paragraphs [0045]-[0047].

The results of the diesel flow test are shown in Table 5, with thedehydration time measured in minutes (min) and the thickness of the plugformed by the dehydrated pill measured in mm:

TABLE 5 Results of Diesel Flow Time Test Diesel Flow Test (150 ccdiesel, 100 psi Pressure, Room Temperature)- API Test ApparatusParameters Test-1 Test-2 Test-3 Effluent Time (min) <1 <1 <1 DepositedPlug 37 38 37 Thickness (mm)

As shown in Table 5, in each test the diesel exited the plug matrix inless than 1 minute (other than the minimal amounts of diesel absorbed bythe plug). Here again, the behavior of the diesel and plug matrix issimilar to the residual hydrocarbon in place of a reservoir, furtherdemonstrating that example LCM formulation has the ability to form dualfunctional permeable plugs that prevent the loss of whole mud but enablehydrocarbon production from conductive fractures and permeable channels.

Another dehydration test was performed on the example LCM formulationusing a 2 millimeter (mm) slotted metal disc and a Permeability PluggingTester (also referred to as a “PPT” or “Pore Plugging Test” apparatus)manufactured by OFI Testing Equipment, Inc., of Houston, Tex., USA, tosimulate a relatively large fracture bounded by a group of relativelysmall fractures (for example, fractures of about 2 mm). The conventionalcell of the Permeability Plugging Tester used in the plugging efficiencytest may be operated up to 2,000 pounds-per-square inch differential(psid) and 500° F. (260° C.). The 2 mm slotted metal disc was used asthe filter medium of the Permeability Plugging Tester in the pluggingefficiency test. The dehydration test was performed at a temperature ofabout 100° C. to simulate an equivalent bottom hole temperature of areservoir, and at a pressure of about 500 psid.

The example LCM formulation was tested using the Permeability PluggingTester apparatus and the following plugging efficiency test procedure:

1. Set the temperature controller/thermostat to the testing temperature;

2. Check the condition of the O-rings in the groove at the top of thetest cell of the Permeability Plugging Tester apparatus and in the cellend cap and replace the O-rings if needed;

3. Apply a thin coating of high temperature grease to all the O-rings,including the two O-rings on the piston of the Permeability PluggingTester apparatus;

4. Screw the T-bar of the Permeability Plugging Tester apparatus intothe piston, install into the bottom end of the test cell, position thepiston about 1 inch into the cell bore, and remove the T-bar;

5. Add a volume of hydraulic oil to the test cell using the hydraulichand pump of the Permeability Plugging Tester apparatus;

6. Install all the O-rings and secure the end cap of the cell inposition such that oil flows from the hole in the end cap to ensure noair is trapped;

7. Install the valve stem into the bottom end cap of the cell, tightenthe valve stem, and disconnect from the hydraulic hand pump of thePermeability Plugging Tester apparatus;

8. Place the cell upright on a suitable stand;

9. Placing about 350 cc of the prepared example LCM formulation into thetest cell;

10. Install an O-ring into the top of the cell below the 2 mm slotteddisc;

11. Place the 2 mm slotted disc on top of the O-ring;

12. Insert the end cap on the top of the disc, screw down the threadedretaining ring, and fully tighten;

13. Tighten the top stem of the test cell;

14. Place the cell into the heating jacket of the Permeability PluggingTester apparatus;

15. Connect a pressure hose from the hydraulic hand pump to the bottomof the test cell via a quick connector and ensure the bottom stem isclosed;

16. Connect the back pressure hose/sample collector to the top stem ofthe test cell, ensuring that the locking pin is in place, close thepressure relief valve on the side of the hydraulic hand pump, apply thetesting pressure via the back pressure regulator to the top of the testcell, and close the top valve.

17. Place a thermometer into the hole at the top of the test cell. waituntil the testing temperature is reached, and monitor the cell pressurewhile heating and bleed off pressure if necessary by opening thepressure relived valve on the side of the hydraulic hand pump;

18. Once the test sample has reached the testing temperature, pump thehydraulic hand pump until the pump gauge shows the testing pressure plusthe required back pressure;

19. Apply the required back pressure to the top of the cell, open thetop valve, and pump the hydraulic hand pump to reestablish the testingpressure;

20. Measure the dehydration time of the pill (that is, the time for thefluid (about 350 cc) to be expelled) collect fluid from the backpressure collector in a container.

Table 6 shows the results of the dehydration test using the PPTapparatus, with expelled volume measured in cubic centimeter (cc), thetime in minutes, and the plug thickness in mm. It should be noted thatthe time required to expel the fluid includes the interruption timerequired to maintain the pressure using the hand pump:

TABLE 6 Results of Dehydration Test Simulating Relatively LargeFractures Bounded by a Group of Relatively Small Fractures DehydrationTest (500 psid Pressure, 100° C. Temperature)-PPT Test ApparatusExpelled fluid volume Time Required to (cc) Expel (min) Plug Thickness(mm) 200 27 54

An initial spurt loss of about 2 cc to about 3 cc was observedimmediately after application of the 500 psid pressure via the handpump. After the initial sport loss, solids-free colored water wasexpelled due to the de-coloration of the date tree-based fibers used inthe example LCM formulation.

FIG. 5 is a photograph 500 of the plug formed in the PPT cell after thedehydration test according to the procedure described supra. Afterdismantling the PT cell, the plug formed was found to be equal to theinner diameter of the PPT cell, thus simulating a big fracture formedand in fluid connection with the small fractures represented by the 2 mmslots. As shown in Table 6, the plug formed by complete dehydration ofthe example LCM formulation occurred in about 27 minutes. However, ifthe time spent maintaining the pressure using the hand pump is excluded,the dehydration time is less than about 27 minutes. FIG. 5 illustratesthe ability of the example LCM formulation to form a plug in fracturedzones bounded by relatively small fractures. The application of the 500psid pressure allowed the formation of a mechanically stable plug withadequate compressive and shear strength. As will be appreciated, as plugthickness is a factor in the creation of stable seal in fractures, agreater concentration of the example LCM formulation may be used in losszones having relatively large fractures.

After the initial spurt loss, the colored fluid (due to thede-coloration of the date tree fibers) indicates the ability of the plugformed by the example LCM formulation to prevent loss of while mud whiledrilling. Moreover, the infiltration of the colored water through theplug indicates the ability of the example LCM formulation to provide forthe production of hydrocarbons through the plug matrix during theproduction phase of a well.

Ranges may be expressed in the disclosure as from about one particularvalue, to about another particular value, or both. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value, to the other particular value, or both, along withall combinations within said range.

Further modifications and alternative embodiments of various aspects ofthe disclosure will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the embodiments described inthe disclosure. It is to be understood that the forms shown anddescribed in the disclosure are to be taken as examples of embodiments.Elements and materials may be substituted for those illustrated anddescribed in the disclosure, parts and processes may be reversed oromitted, and certain features may be utilized independently, all aswould be apparent to one skilled in the art after having the benefit ofthis description. Changes may be made in the elements described in thedisclosure without departing from the spirit and scope of the disclosureas described in the following claims. Headings used described in thedisclosure are for organizational purposes only and are not meant to beused to limit the scope of the description.

What is claimed is:
 1. An altered drilling fluid, comprising: a drillingfluid; and a lost circulation material (LCM) composition, wherein theLCM composition comprises: a carrier fluid; a particulate materialcomprising a clay; a viscosifier; and a fibrous material comprising datetree waste fibers.
 2. The altered drilling fluid of claim 1, wherein thecarrier fluid comprises water.
 3. The altered drilling fluid of claim 1,wherein the viscosifier comprises a cellulosic microfiber.
 4. Thealtered drilling fluid of claim 1, wherein the date tree waste fiberscomprise date tree rachis fibers, date tree leaf fibers, or acombination thereof.
 5. The altered drilling fluid of claim 1, whereinthe clay comprises calcium montmorillonite clay.
 6. The altered drillingfluid of claim 5, wherein the calcium montmorillonite clay comprises anamount in the range of 3 weight % of the total weight (w/w %) to 6 w/w %of the LCM composition.
 7. The altered drilling fluid of claim 1,wherein the date tree waste fibers comprise an amount in the range of 6weight % of the total weight (w/w %) to 9 w/w % of the LCM composition.